Wrinkles, that is, creases or chicken paw prints, have always been a difficult problem to solve in the dyeing and finishing of chemical fiber or cotton knitted fabrics, especially for stretch knitted fabrics containing spandex. In view of the high elasticity and extension of spandex itself nature, making it easier to produce or form new wrinkles during processing. In severe cases, it is difficult to meet the requirements even after repairs, which will have a certain impact and loss on the product quality and efficiency of the factory.
Causes of wrinkles
The main reason for wrinkles in ammonia-containing stretch knitted fabrics is that the fabric in the cylinder is in a folded and squeezed state when the temperature rises and falls. When the speed is too fast, the fibers shrink unevenly in a short period of time, and the coils will shift and deform to form wrinkles; at the same time, during the processing and post-setting of the fabric after it comes out of the vat, if the temperature of the cloth itself is too high or the cooling is not enough, and the spandex is first Rebound shrinkage coupled with long-term stacking pressure can also easily lead to wrinkles.
Preventive measures
1. Strengthen pre-treatment equipment and operations: ammonia-containing elastic fabrics must be strengthened or improved regardless of whether they are refined in the form of open width or rope. The synchronization between the guide rollers of the equipment prevents the cloth surface from being pulled and squeezed. Finally, room temperature water washing is used to prevent overheating and wrinkles caused by excessive, too high, or too long cloth accumulation.
2. Strictly control the pre-setting process: pre-setting can prevent curling, wrinkling and stabilize the width. Without affecting the elasticity and feel of the spandex, a slightly higher temperature can be used for shaping, such as polyurethane. The type can be controlled at 190-195℃, the nylon ammonia type 185-190℃, the cotton ammonia type 180-185℃, and the vehicle speed is generally 15-20m. At the same time, keep the fabric surface flat to prevent shrinkage and wrinkles.
3. Adjust the nozzle pressure and lifting roller speed during dyeing: coordinate the two according to the weight of the fabric to prevent wrapping, pressing cylinders, and cloth clogging. If necessary, increase the liquor ratio appropriately. Reduce the amount of the tank and add anti-wrinkle agent in the bath or increase the cloth speed, etc.
4. Control the heating and cooling speed: Strictly operate according to the computer program settings, strengthen process discipline, control the temperature not to exceed 1-1.5℃/min, and prevent excessive speed from causing fiber aggregation and shrinkage to cause a large number of wrinkles.
5. Doing a good job in post-shaping can effectively reduce the dropping temperature, and appropriately increasing the setting temperature can help eliminate false wrinkles and slight wrinkles in the previous process. Generally, depending on the type, the controlled temperature of chemical fibers can be 10-20°C lower than the predetermined temperature, and that of cotton can be lowered by 20-30°C. At the same time, it is best to blow cold air and cool down the cooling roller at the cloth outlet to ensure that the cloth surface is below 50°C, otherwise the temperature will be lower than the predetermined temperature. Heat pressing can create new wrinkles.
6. In addition, if the unwinding loose cloth in the front line is left for too long, the spandex will shrink and cause edge wrinkles. It must be booked in time to avoid it. Including dehydration after dyeing, it must not be too dry or too long. Remove to 70% and leave it for no more than 2-3 hours. </p
